The present invention relates to a quick adjusting device for bicycle brake cables, and especially to a device having a substantially S-shaped base, a camshaft, a worm, a worm gear shaft, and a pulley. Two plates are formed on the bottom of the base and define an area. The worm gear and the wheel, together, clamp a brake cable. The wheel is located on the camshaft. The brake cable is driven by the worm to move upwards or downwards via the worm gear and the wheel. A pulley is received in an area of the base and used to adjust the relative position of the left side and the right side brake arms.
Conventional bicycles use cross-type brake arm in their brake devices. In another type of bicycle brake device, the brake arms is installed independently on a right side and a left side of the front and rear forks of the bicycles. The brake cables of these bicycle brake devices are easy to loosen but not easy to adjust after it has been used for a period of time. Furthermore, if two brake arms of the bicycle are not in the right position, it is very difficult to adjust.